1. Field of the Invention
The present invention relates to a DNA aptamer specifically binding to human cardiac troponin I, and a composition and a diagnostic kit for the diagnosis of acute cardiovascular diseases, comprising the same.
2. Description of the Related Art
Troponin is a complex of three regulatory proteins (troponin C, troponin I and troponin T) that is attached to the protein tropomyosin and lies within the groove between actin filaments in muscle tissue to regulate the contraction and relaxation of muscle cells. When the intracellular levels thereof rise, Ca2+ is bound to specific sites on Troponin C to produce a conformational change in Troponin I so that myosin can attach to the actin filament active sites, giving rise to the contraction of the muscle. This action is observed in both skeletal and cardiac muscles. The length of the amino acid sequence of Troponin I and Troponin T that act on cardiac muscle are different from the corresponding ones expressed in skeletal muscle.
The expression level of cardiac troponin I is known to rapidly increase upon the outbreak of acute cardiovascular diseases. Thus, the detection of this protein is very important for the initial diagnosis of acute cardiovascular diseases.
An aptamer is a single strand DNA (ssDNA) or RNA (ssRNA) that binds to a specific target. Thanks to their high affinity and stability to a specific target, they have recently been extensively developed and actively applied to the therapy and sensors for diagnosis of diseases. The synthesis of aptamers can be relatively simple, and cells, proteins and even small organic substance can be utilized as their targets, which allows for the development of new detection methods. In addition, aptamers find a wide range of applications in various fields, including the development of therapeutics, drug delivery systems, biosensors for diagnosis, etc. because their specificity and stability are superior to those of the antibodies that were developed previously.
Antibodies developed for diagnostic use are prepared using the immune system and thus suffer from the disadvantage of their preparation consuming a lot of time and expense, comparatively. Further, they are proteins that have poor stability, compared to aptamers, DNA or RNA, which may act as an obstruction to the development of highly sensible sensors.
Although many detection systems for troponin I have been developed on the basis of antibodies to troponin I, as mentioned above, they are subject to a lot of limitations. There is therefore a need for a detection system that is more stable and which can be operated at low cost and effectively diagnoses acute cardiovascular diseases in an early stage.